Arthroplasty is an orthopedic surgical procedure in which a dysfunctional or arthritic joint surface is replaced, remodeled or redesigned to alleviate pain, restore range of motion or to fix physical joint damage caused by a fracture. There are several surgical options available for a dysfunctional or arthritic hip joint. For example, Total Hip Replacement (“THR”) surgery, also known as hip arthroplasty, is a surgical procedure wherein the proximal femur, with its femoral head and neck, is removed and a prosthetic device (or stem) having a prosthetic femoral head is implanted into the femur. The acetabulum, or hip socket, is also replaced or modified to accept a cup. The cup is configured to receive the prosthetic head. The prosthetic device (or stem) is typically made of titanium or a titanium alloy. The head may be made of a biocompatible plastic, ceramic or other suitable material. The cup may be made of a biocompatible plastic or other suitable material. The prosthetic device and the cup are typically anchored to the bone with bone cement.
Hip Resurfacing is another form of arthroplasty that was developed as an early intervention alternative to THR. In a Hip Resurfacing Surgery (“HRS”), the acetabulum is replaced, modified, or resurfaced to accept the cup, which is configured to receive the head. However, the proximal femur and, more specifically, the femoral head and neck, are not removed. Instead, the femoral head is resurfaced with, or otherwise modified to accept, a femoral head cap or other hip surface replacement.
Several factors, such as potential muscle damage or effect on the blood supply, are considered when choosing a surgical approach for a HRS or hip arthroplasty in general. Typically, a posterior approach or an anteriorlateral approach is utilized, but other approaches, such as a lateral approach or an anterior approach, may also be utilized. The posterior approach is traditionally known as a muscle sparing approach and is more common than the anteriorlateral approach, which is traditionally known as a muscle compromising approach. The posterior approach or anteriorlateral approach generally refers to the side to which the hip is dislocated as opposed to the location of the surgical incision. Regardless of which approach is used, the incision is on the side (lateral).
In some cases, the anteriorlateral approach may have a decreased rate of hip dislocation. This is important because in HRS, femoral neck impingement might occur more readily as a result of the absence of the head and neck offset that is normally associated with the original femoral components. Contact between the pelvic bone and the femoral neck may not only dislocate the femoral head but may also potentially become the origin of a stress-riser leading to a femoral neck fracture. The anteriorlateral approach may also preserve blood flow more consistently to the femoral head in comparison to the posterior approach because the approach produces less disruption to the blood flow in the femoral head-neck junction as reflected by a lower incidence of fracture of the femoral neck and avascular necrosis.
Typically, HRS utilizes a three part tool to properly place the femoral head cap through the center of the femoral head and along the central axis of the femoral neck. The tool is drilled into the femoral neck at a point that is estimated by observation of x-ray scans of the patient's femur. During surgery, this point is determined with a ruler and measured from the level of the greater trochanter of the femur. The three part tool is then drilled into the measured point. However, this three-part tool, the x-ray scan and hand measuring techniques are inaccurate and increase the error rate or potential for error in a hip resurfacing surgery.
Inaccurate drilling can result in a weakened femoral neck and/or damage to the artery extending through the femoral neck to supply the femoral head. Damage to this blood supply can lead to avascular necrosis.
There is a need in the art for a hip resurfacing surgical guide tool that increases accuracy, can be used with any surgical approach and reduces the potential for error associated with drilling through the femoral head and neck when preparing for hip surface replacement. There is also a need in the art for a method of manufacturing such a surgical guide tool.